1. Field of the Invention
The present invention relates to a system and method for the utilization of heat sources with moderate to low initial temperature, such as geothermal waste heat sources or other similar sources.
More particularly, the present invention relates to a system and method for the utilization of heat sources with moderate to low initial temperature, such as geothermal waste heat sources or other similar sources involving a multi-staged heating process and at least one separation step to enrich the working fluid which is eventually fully vaporized for energy extraction.
2. Description of the Related Art
In the prior art, U.S. Pat. No. 4,982,568, a working fluid is a mixture of at least two components with different boiling temperatures. The high pressure at which this working fluid vaporizes and the pressure of the spent working fluid (after expansion in a turbine) at which the working fluid condenses are chosen in such a way that at the initial temperature of condensation is higher than the initial temperature of boiling. Therefore, it is possible that the initial boiling of the working fluid is achieved by recuperation of heat released in the process of the condensation of the spent working fluid. But in a case where the initial temperature of the heat source used is moderate or low, the range of temperatures of the heat source is narrow, and therefore, the possible range of such recuperative boiling-condensation is significantly reduced and the efficiency of the system described in the prior art diminishes.
Thus, there is a need in the art for a new thermodynamic cycle and a system based thereon for enhanced energy utilization and conversion.